Deer are vegetarians who feed on moss, bark, buds, leaves, or water plants. They are usually very timid animals, and they depend on their speed for safety. They generally feed at night. They have very good eyesight, and their senses of hearing and smell are so sharp that they are able to detect danger easily. Deer vary in size from the little pudu, which is only a foot tall, to the great moose, which may weigh more than 450 kilograms.